Conventionally, there is a known decorative board with fireproof performance and non-combustibility (hereinafter referred to as a “non-combustible decorative board”). Such a non-combustible decorative board includes a core layer, which is a prepreg formed by impregnating an inorganic fiber nonwoven fabric with a slurry including phenol resin or melamine resin as a binder component (see Patent Documents 1-3).    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-230611    Patent Document 2: Japanese Unexamined Patent Application Publication No. 10-44323    Patent Document 3: Japanese Unexamined Patent Application Publication No. 64-56540